This invention relates generally to coin operated devices and, more particularly, to an improved coin acceptor mechanism and a method of providing more accurate coin recognition by reducing the effects of electrical noise.
Coin acceptor mechanisms are commonly found in a vast array of devices including coin operated laundry machines, vending machines, pay telephones and video game or slot machines. These machines are typically operable only upon insertion of a predetermined designated amount of currency. In all such devices it is important to accurately recognize the input of proper coins or other tokens while automatically rejecting the input of slugs, pennies or other undesired objects. One common type of coin acceptor mechanism for accomplishing this task is illustrated schematically at 10 in FIG. 1. This type of device typically includes a mechanical coin acceptor 12 which is electrically connected to an electronic processor 14 via a set of leads or wires 16. A coin 18, or other token, is deposited into a designated slot 20 and is guided mechanically along a path 22. Coin path 22 is appropriately configured so as to guide coin 18 in a desired orientation through a coin read station 24, prior to deposit into a coin collection area 26, or otherwise rejection to a coin return (not shown).
The coin read station 24 may include a coin feeler spring/micro switch assembly 26 as shown in FIG. 2, or any other similar device which is capable of producing signals of two different conductive states. Switch 26 sends an electrical signal of one such conductive state over lines 16 to microprocessor 14 when in physical contact with a falling coin 18 and outputs at another state when not in contact with coin 18. In a like fashion, an optical reader such as a photo-interrupter or similar sensor device could alternately be used to provide the coin presence/absence signal over lines 16 whenever a coin or other object is detected/not detected at a given point.
Typically, microprocessor 14 is programmed with a methodology for analyzing the incoming electrical signal in order to assess when a valid coin has been deposited. To accomplish this, the microprocessor 14, upon first indication of coin presence, can check the signal on lines 16 a predetermined number of times for repeated indication of the presence of a coin. The number of instances checked is dependent upon factors such as the size of the coin and the speed at which it passes through the read station. In this example, there is a separate coin read station for each type of allowed coin input and each checks for only one type of coin but it will become readily apparent that the present invention is equally well adapted for use in other types of coin acceptor mechanisms as well.
However, as with any such device, real world conditions can cause the mechanism 10 to incorrectly accept an improper deposit or incorrectly reject a proper deposit. One common reason for this occurrence is a physical bouncing of the switch 26 as the coin 18 passes thereby. For instance, the force exerted by the falling coin on the mechanical spring can cause it to "bounce" thereby resulting in a situation wherein the signal on line 16 may be temporarily "interrupted" or wherein the sensor produces a signal of the incorrect conductive state. If the signal is interrupted at one or more points in time when microprocessor 14 is checking for the presence of a coin, the coin may be incorrectly rejected and returned. Rough surfaces on the coin, as well as various other conditions, may also cause the same problem.
The present invention provides an effective but simple solution to this problem which can be implemented inexpensively in microprocessor 14. As a coin passes into the read station, an "in slot" counter, preferably part of microprocessor 14, counts the number of two millisecond samples that are valid during a preset period of time. In other words, microprocessor 14 checks for two millisecond pulses occurring at the same time switch 26 outputs a signal of a particular conductive state, deemed indicative of coin presence. Any coincidence of a two millisecond pulse and an invalid coin present signal is ignored. At the end of a second predetermined time period, an "out of slot" counter, also preferably implemented as part of microprocessor 14, counts the number of samples coincident with an "out of slot" signal or a sensor 26 output signal at the other conductive state, that which is indicative of coin absence. In this manner, false rejections of valid coins are reduced. This results in a more accurate method of coin recognition which is less adversely affected by the electrical noise caused primarily by switch bounce.
These and other features and advantages of the present invention will become apparent upon review of the following disclosure, taken in conjunction with the accompanying drawings.